Effect of stool storage at room temperature on salmonella isolation from faeces

Stools, known to have contained salmonellas were cultured in three enrichment media on arrival at the laboratory. The three media were laboratory prepared selenite F, laboratory prepared Muller-Kauffmann tetrathionate and commercially obtained Oxoid Muller-Kauffmann tetrathionate (CM343). Where faecal samples were sufficiently large, they were stored at room temperature and re-examined using the same three enrichment broths. Whether fresh or stored stools were investigated, the laboratory prepared media were significantly more efficient than the commercial medium. In a straight comparison of the two laboratory prepared media, no significant difference in efficiency was evident with fresh stool samples. With stored specimens, however, Muller-Kauffmann tetrathionate was significantly better than selenite F. This finding might be relevant in examining samples delayed in the post.